In recent years, the application of a liquid crystal display device (LCD), an organic light emitting device (OLED), and the like has expanded, and the LCD or the like is used also in various types of displays used outdoors.
For example, the LCD or the like is widely used in an instrument panel of a vehicle, a ship, an airplane, or the like, an on-vehicle car navigation system, a digital camera, a mobile apparatus such as a mobile phone or a personal computer, digital signage used in, for example, a building or a supermarket, or the like. In such an electronic apparatus, a touch panel which serves as a display and input means is widely used.
As types of touch panels, those of an optical type, an ultrasonic type, an electromagnetic induction type, a resistive film type, or a capacitance type are generally used. However, for a combination with a small liquid crystal display, a resistive film type touch panel is often used. The resistive film type touch panel is an input switch using a transparent conductive film as a conductor, and is structured such that two transparent conductive films face each other via a spacer. A pressure made by a stylus or a finger brings the electrode faces into contact with each other to cause conduction, whereby position detection can be performed.
In contrast, a capacitance type touch panel allows detection of multiple points, so-called multi-touch, which cannot be realized by an ordinary resistive film type touch panel, and thus, the capacitance type touch panel has been attracting attention in recent years. With respect to the above-described transparent conductive film, a transparent conductive film is formed on a base material, to be subjected to annealing treatment (heat treatment) at a predetermined temperature (for example, about 150° C.) in order to obtain durability, whereby the transparent conductive film is crystallized.
However, in a conventional capacitance type touch panel, transparency differs between a portion where a transparent electrode is present and a portion where a transparent electrode is not present, and thus, difference in brightness or tint on the display screen is caused. Accordingly, a user can recognize the presence of the transparent electrode, which is a problem in terms of appearance and displaying quality of the display. As a technique for improving this problem to some extent, a method has also been taken in which the gap between adjacent transparent electrodes in the vertical direction or in the horizontal direction is narrowed to make the transparency of the screen come close to a constant level. However, in such a touch panel, there occurs another problem that, due to the narrow gap between adjacent transparent electrodes in the vertical direction or in the horizontal direction, when a peripheral portion of a key is touched, a key adjacent thereto is erroneously input.
In order to solve this problem, for example, Patent Literature 1 discloses an erroneous input preventing touch panel. In this erroneous input preventing touch panel, the gap between a vertical transparent electrode 2 and a dummy electrode 4 is set to be not greater than about 0.6 mm. Consequently, transparency comes close to a constant level.
Patent Literature 2 discloses a touch panel device. In this touch panel device, the intervals between vertical transparent electrodes 2a to 2n and dummy electrode arrays 4a to 4n, are narrow, and each of the dummy electrode arrays 4a to 4n is present in the gap delimited by electrodes adjacent thereto, and thus, transmittance comes close to a constant level.